AquaVIT-4: International Intercomparison of atmospheric water-vapor instruments

PI: Dr. M. Ghysels-Dubois, Groupe de Spectrométrie Moléculaire et Atmosphérique (GSMA, UMR CNRS 7331), CNRS, France. Email:

The AquaVIT-4 campaign aims to compare state of the art and new atmospheric hygrometers with each other and with traceable humidity standards at the aerosol and cloud simulation chamber AIDA (Karlsruhe Institute of Technology, Germany, ). 

This campaign occurred in the frame of the HEMERA project. The campaign has been held from March 21, 2022 to April 8, 2022. This campaign is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730997 and that is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRAIA-2020-1, Grant Agreement number:101008004.”

Figure 2: Group picture of the AQUAVIT-4 campaign on April 8, 2022, last day of the campaign.

The campaign started on March 21, 2022 with the installation of Pico-Light H2O, ALBATROSS and the NASA DLH hygrometers. On the 24th and 25th, first tests were realized to check for the proper operation of the integrated instruments. Simulated conditions included room temperature (296K) test at pressure varying from 20 to 800 hPa, followed on the 25th by cooled conditions at 234 K and pressures between 20 to 400 hPa.

The SAWfPhy instrument was installed on March 28, 1 m away from Pico-Light, in the bottom of the main vessel.

The series of experiments has started on March 29.

Datasets will be publicly available soon.


Figure 1: Picture of the AIDA facility.

The present campaign is built in the frame of the HEMERA H2020 european project, a new research infrastructure involving a large community in balloon-borne researches. In the frame of the WP 11 “Innovation on sensors and algorithms for balloon-borne research”, this proposal focuses on the JRA 2.1 and 2.2, which aims at defining standards and protocols for balloon measurements relevant for Copernicus and a set of Light Innovative Instruments (SLII) for transnational access (TNA) payload and data during TNA flights. AquaVIT-4 aims to support newly developed european hygrometers in their calibration efforts against reference and well-known instruments.

This campaign would be one piece of a larger project which aims at including metrological institutes to help defining good practices and standards for essential climate variables, facing the need of increasingly accurate and precise atmospheric data.

The campaign practical objectives are:

  • To provide a continued basis for quality control of airborne hygrometer measurements.
  • To document the improvement of existing hygrometers and the allow the testing of new instruments related to the JRA 2.1 / 2.2 of Hemera EU project (

The campaign will be split into two phases :

  • Quick look data (week 1): Preliminary measurements will be made available to the referees as soon as possible following each day’s experiments (<24 h). This step will allow, in case of difficulties, to suggest corrections to data processing, instrument configuration, or instrument operation to improve the overall outcome of the intercomparison.
  • Blind comparison (week 2) : blind measurements will be quickly release (within 2 months), together with preliminary data to be made available only to the referees (O. Möhler, K. Rosenloff , M. Fujiwara and E. Georgin (to be confirmed)) who are not affiliated with any participating instrument team. The referee board, will therefore perform a short evaluation (within 2 months).

At the end of the short evaluation period, datasets will be release to all participants. After careful checking from respective participants, final datasets will be made available to the AERIS data portal.

Participants :

AquaVIT-4 gathers 22 participants from 9 laboratories in the USA, Europe and Russia. A list of the participants is shown in the table below together with the hygrometers and their location in the chamber.

Potential participantAffiliationInstrumentLocation at AIDA*
Harald Saathoff,
Robert Wagner
Ottmar Möhler
KIT, DTDL (1370 nm) for measurements in AIDA (gas phase water only) APicT

TDL (1370 nm) for measurements outside AIDA (total water) APeT

Harald Saathoff,
Robert Wagner
Ottmar Möhler
KIT, DDew point mirror MBW-373LX, FTIR (ice water content)
Nadir Amarouche,
F. Frérot,
M. Ghysels-Dubois#,
G. Durry
Albert Hertzog,
Claire Cenac,
Julio Lopez,
Paul Monnier
LMD, (DPAO), Palaiseau Cedex, FRSAWfPHY -IN1
Ivan Formanyuk,
Alexey Lykov
(canceled due to the war of Ukraine)
Central Aerological Observatory (CAO), Moscow, RUFLASH (A) – Canceled due to the war in Ukraine3
Glenn DiskinNASA Langley, USADiode Laser Hygrometer (DLH)2
Manuel Béla Tuzson, Simone Brunamonti
EMPA, Dübendorf, CHLightweight Mid-IR Laser Spectrometer
Ottmar MöhlerKITPresent at AIDA only until April 1st
Karen RosenloffNOAA
Masatomo FujiwaraHokkaido University

*Options: 1) inside the vessel, 2) outside the vessel in the cold part, 3) heated sampling line to the warm laboratory.#PI.


Banerjee, A., Chiodo, G., Previdi, M., Ponater, M., Conley, A. J., and Polvani, L. M.: Stratospheric water vapor: an important climate feedback, Clim Dyn, 53, 1697–1710,, 2019.

Behera Abhinna K., Rivière Emmanuel D., Marécal Virginie, Rysman Jean‐François, Chantal Claud, Sèze Geneviève, Amarouche Nadir, Ghysels Mélanie, Khaykin Sergey M., Pommereau Jean‐Pierre, Held Gerhard, Burgalat Jérémie, and Durry Georges: Modeling the TTL at Continental Scale for a Wet Season: An Evaluation of the BRAMS Mesoscale Model Using TRO‐Pico Campaign, and Measurements From Airborne and Spaceborne Sensors, Journal of Geophysical Research: Atmospheres, 123, 2491–2508,, 2018.

Berthet, G., Renard, J.-B., Ghysels, M., Durry, G., Gaubicher, B., and Amarouche, N.: Balloon-borne observations of mid-latitude stratospheric water vapour: comparisons with HALOE and MLS satellite data, J Atmos Chem, 70, 197–219,, 2013.

Dessler, A. E.: Observations of Climate Feedbacks over 2000–10 and Comparisons to Climate Models, J. Climate, 26, 333–342,, 2013.

Dessler, A. E. and Wong, S.: Estimates of the Water Vapor Climate Feedback during El Niño–Southern Oscillation, J. Climate, 22, 6404–6412,, 2009.

Dessler, A. E., Zhang, Z., and Yang, P.: Water-vapor climate feedback inferred from climate fluctuations, 2003–2008, 35,, 2008.

Dessler, A. E., Schoeberl, M. R., Wang, T., Davis, S. M., and Rosenlof, K. H.: Stratospheric water vapor feedback, PNAS, 110, 18087–18091,, 2013.

Durry, G., Amarouche, N., Joly, L., Liu, X., Parvitte, B., and Zéninari, V.: Laser diode spectroscopy of H<Subscript>2</Subscript>O at 2.63 μm for atmospheric applications, Appl. Phys. B, 90, 573–580,, 2008a.

Durry, G., Amarouche, N., Joly, L., Liu, X., Parvitte, B., and Zéninari, V.: Laser diode spectroscopy of H2O at 2.63 μm for atmospheric applications, Appl. Phys. B, 90, 573–580,, 2008b.

Dvortsov, V. L. and Solomon, S.: Response of the stratospheric temperatures and ozone to past and future increases in stratospheric humidity, J. Geophys. Res., 106, 7505–7514,, 2001.

Fahey, D. W., Gao, R.-S., Möhler, O., Saathoff, H., Schiller, C., Ebert, V., Krämer, M., Peter, T., Amarouche, N., Avallone, L. M., Bauer, R., Bozóki, Z., Christensen, L. E., Davis, S. M., Durry, G., Dyroff, C., Herman, R. L., Hunsmann, S., Khaykin, S. M., Mackrodt, P., Meyer, J., Smith, J. B., Spelten, N., Troy, R. F., Vömel, H., Wagner, S., and Wienhold, F. G.: The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques, Atmos. Meas. Tech., 7, 3177–3213,, 2014.

Forster, P. M. de F. and Shine, K. P.: Stratospheric water vapour changes as a possible contributor to observed stratospheric cooling, 26, 3309–3312,, 1999.

Gettelman, A., Hegglin, M. I., Son, S.-W., Kim, J., Fujiwara, M., Birner, T., Kremser, S., Rex, M., Añel, J. A., Akiyoshi, H., Austin, J., Bekki, S., Braesike, P., Brühl, C., Butchart, N., Chipperfield, M., Dameris, M., Dhomse, S., Garny, H., Hardiman, S. C., Jöckel, P., Kinnison, D. E., Lamarque, J. F., Mancini, E., Marchand, M., Michou, M., Morgenstern, O., Pawson, S., Pitari, G., Plummer, D., Pyle, J. A., Rozanov, E., Scinocca, J., Shepherd, T. G., Shibata, K., Smale, D., Teyssèdre, H., and Tian, W.: Multimodel assessment of the upper troposphere and lower stratosphere: Tropics and global trends, 115,, 2010.

Ghysels, M., Riviere, E. D., Khaykin, S., Stoeffler, C., Amarouche, N., Pommereau, J.-P., Held, G., and Durry, G.: Intercomparison of in situ water vapor balloon-borne measurements from Pico-SDLA H2O and FLASH-B in the tropical UTLS, Atmos. Meas. Tech., 9, 1207–1219,, 2016.

Hall, E. G., Jordan, A. F., Hurst, D. F., Oltmans, S. J., Vömel, H., Kühnreich, B., and Ebert, V.: Advancements, measurement uncertainties, and recent comparisons of the NOAA frost point hygrometer, Atmos. Meas. Tech., 9, 4295–4310,, 2016.

Hurst, D. F., Hall, E. G., Jordan, A. F., Miloshevich, L. M., Whiteman, D. N., Leblanc, T., Walsh, D., Vömel, H., and Oltmans, S. J.: Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE-2009, Atmos. Meas. Tech., 4, 2777–2793,, 2011a.

Hurst, D. F., Oltmans, S. J., Vömel, H., Rosenlof, K. H., Davis, S. M., Ray, E. A., Hall, E. G., and Jordan, A. F.: Stratospheric water vapor trends over Boulder, Colorado: Analysis of the 30 year Boulder record, 116,, 2011b.

Hurst, D. F., Oltmans, S. J., Vömel, H., Rosenlof, K. H., Davis, S. M., Ray, E. A., Hall, E. G., and Jordan, A. F.: Stratospheric water vapor trends over Boulder, Colorado: Analysis of the 30 year Boulder record, 116,, 2011c.

Hurst, D. F., Lambert, A., Read, W. G., Davis, S. M., Rosenlof, K. H., Hall, E. G., Jordan, A. F., and Oltmans, S. J.: Validation of Aura Microwave Limb Sounder stratospheric water vapor measurements by the NOAA frost point hygrometer, 119, 1612–1625,, 2014.

Hurst, D. F., Read, W. G., Vömel, H., Selkirk, H. B., Rosenlof, K. H., Davis, S. M., Hall, E. G., Jordan, A. F., and Oltmans, S. J.: Recent divergences in stratospheric water vapor measurements by frost point hygrometers and the Aura Microwave Limb Sounder, Atmos. Meas. Tech., 9, 4447–4457,, 2016.

Jensen, E., Rosenlof, K., Hurst, D., Sayres, D. S., Smith, J., and Herman, R.: SPARC Water Vapor Assessment: Comparison of in situ and Aura MLS stratospheric water vapor measurements from 2004 through 2011, 2011.

Khaykin, S. M., Engel, I., Vömel, H., Formanyuk, I. M., Kivi, R., Korshunov, L. I., Krämer, M., Lykov, A. D., Meier, S., Naebert, T., Pitts, M. C., Santee, M. L., Spelten, N., Wienhold, F. G., Yushkov, V. A., and Peter, T.: Arctic stratospheric dehydration – Part 1: Unprecedented observation of vertical redistribution of water, Atmos. Chem. Phys., 13, 11503–11517,, 2013.

Kiehl, J. T. and Trenberth, K. E.: Earth’s Annual Global Mean Energy Budget, Bull. Amer. Meteor. Soc., 78, 197–208,<0197:EAGMEB>2.0.CO;2, 1997.

Kley, D., Russell, J. M., Phillips, C., and Organization (WMO), W. M.: WCRP, 113. SPARC assessment of upper tropospheric and stratospheric water vapour, WMO, Geneva, 312 p. pp., 2000.

Korotcenkov, G.: Handbook of Humidity Measurement, Volume 1: Spectroscopic Methods of Humidity Measurement, CRC Press, 626 pp., 2018.

Lacis, A. A., Hansen, J. E., Russell, G. L., Oinas, V., and Jonas, J.: The role of long-lived greenhouse gases as principal LW control knob that governs the global surface temperature for past and future climate change, 65, 19734,, 2013.

Lykov, A., Khaykin, S., Yushkov, V., Efremov, D., Formanyuk, I., and Astakhov, V.: Fluorescence Lyman-Alpha Stratospheric Hygrometer (FLASH): application on meteorological balloons, long duration balloons and unmanned aerial vehicles., 40th COSPAR Scientific Assembly, 2014.

Minschwaner, K. and Dessler, A. E.: Water Vapor Feedback in the Tropical Upper Troposphere: Model Results and Observations, J. Climate, 17, 1272–1282,<1272:WVFITT>2.0.CO;2, 2004.

Oltmans, S. J., Vömel, H., Hofmann, D. J., Rosenlof, K. H., and Kley, D.: The increase in stratospheric water vapor from balloonborne, frostpoint hygrometer measurements at Washington, D.C., and Boulder, Colorado, Geophys. Res. Lett., 27, 3453–3456,, 2000.

Randel, W. J., Wu, F., Oltmans, S. J., Rosenlof, K., and Nedoluha, G. E.: Interannual Changes of Stratospheric Water Vapor and Correlations with Tropical Tropopause Temperatures, 61, 2133–2148,<2133:ICOSWV>2.0.CO;2, 2004.

Riese, M., Ploeger, F., Rap, A., Vogel, B., Konopka, P., Dameris, M., and Forster, P.: Impact of uncertainties in atmospheric mixing on simulated UTLS composition and related radiative effects, 117,, 2012.

Rosenlof, K. H. and Reid, G. C.: Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection, 113,, 2008.

Rosenlof, K. H., Oltmans, S. J., Kley, D., Russell, J. M., Chiou, E.-W., Chu, W. P., Johnson, D. G., Kelly, K. K., Michelsen, H. A., Nedoluha, G. E., Remsberg, E. E., Toon, G. C., and McCormick, M. P.: Stratospheric water vapor increases over the past half-century, Geophys. Res. Lett., 28, 1195–1198,, 2001a.

Rosenlof, K. H., Oltmans, S. J., Kley, D., Russell, J. M., Chiou, E.-W., Chu, W. P., Johnson, D. G., Kelly, K. K., Michelsen, H. A., Nedoluha, G. E., Remsberg, E. E., Toon, G. C., and McCormick, M. P.: Stratospheric water vapor increases over the past half-century, Geophys. Res. Lett., 28, 1195–1198,, 2001b.

Scherer, M., Vömel, H., Fueglistaler, S., Oltmans, S. J., and Staehelin, J.: Trends and variability of midlatitude stratospheric water vapour deduced from the re-evaluated Boulder balloon series and HALOE, Atmospheric Chemistry & Physics, 8, 1391–1402, 2008.

Schmidt, G. A., Ruedy, R. A., Miller, R. L., and Lacis, A. A.: Attribution of the present-day total greenhouse effect, 115,, 2010.

Soden, B. J., Jackson, D. L., Ramaswamy, V., Schwarzkopf, M. D., and Huang, X.: The Radiative Signature of Upper Tropospheric Moistening, 310, 841–844,, 2005.

Solomon, S., Rosenlof, K. H., Portmann, R. W., Daniel, J. S., Davis, S. M., Sanford, T. J., and Plattner, G.-K.: Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming, 327, 1219–1223,, 2010.

Vömel, H., Yushkov, V., Khaykin, S., Korshunov, L., Kyrö, E., and Kivi, R.: Intercomparisons of Stratospheric Water Vapor Sensors: FLASH-B and NOAA/CMDL Frost-Point Hygrometer, J. Atmos. Oceanic Technol., 24, 941–952,, 2007.

Wang, Y., Su, H., Jiang, J. H., Livesey, N. J., Santee, M. L., Froidevaux, L., Read, W. G., and Anderson, J.: The linkage between stratospheric water vapor and surface temperature in an observation-constrained coupled general circulation model, Clim Dyn, 48, 2671–2683,, 2017.

Yan, X., Wright, J. S., Zheng, X., Livesey, N. J., Vömel, H., and Zhou, X.: Validation of Aura MLS retrievals of temperature, water vapour and ozone in the upper troposphere and lower–middle stratosphere over the Tibetan Plateau during boreal summer, 9, 3547–3566,, 2016.

Yushkov, V., Astakhov, V., and Merkulov, S.: Optical balloon hygrometer for upper-troposphere and stratosphere water vapor measurements, 439–445,, 1998.